Computer users employ writable and rewritable optical discs for a variety of different purposes. They may save programs or data to the discs, for archival or distribution purposes. In the case of CD-type discs, users may make music CD's that can be played in audio CD players, or save music data files to the CD's, such as MP3 files, that can be played in special-purpose CD players. In the case of DVD-type discs, users have greater storage capacity available to them than with CD-type discs, and may be able to make video DVD's that can be played in stand-alone DVD players.
Many types of optical discs include a data side and a label side. The data side is where the data is written to, whereas the label side allows the user to label the optical disc. Unfortunately, labeling can be an unprofessional, laborious, and/or expensive process. Markers can be used to write on optical discs, but the results are decidedly unprofessional looking. Special pre-cut labels that can be printed on with inkjet or other types of printers can also be used. However, this is a laborious process: the labels must be carefully aligned on the discs, and so on. Special-purpose printers that print directly on the discs can be used, but such printers are fairly expensive.
In the patent application entitled “Integrated CD/DVD Recording and Label” [attorney docket 10011728-1], filed on Oct. 11, 2001, and assigned Ser. No. 09/976,877, a solution to these difficulties is described, in which a laser is used to label optical discs. However, as a laser ages, it tends to lose its ability to write a given sized mark on the label side of an optical disc at a given level of power applied to the laser. Dust or other opaque or light scattering materials may accumulate on the optical system's lens(es), also affecting its ability to write a mark on the disc's label side at a given level of power.
Furthermore, the material used for the label side of an optical disc can vary in photosensitivity, reflectivity, color, as well as in other properties from one type of optical disc to another type of optical disc. Even for discs of the same type, manufacturing variations can cause variations in these or other optical properties from disc to disc, and can even cause variations within a given optical disc. Any or all of these reasons may affect the resulting quality of optical disc labeling using a laser.